Zr alloys for fusion applications

This project is concerned with the design and testing of new Zr alloys for potential use in future fusion reactors. It is incorporated into the EPSRC Fusion Centre for Doctoral Training and will also contribute to the EPSRC programme grant on Zr alloys EP/S01702X/1. Because of their good corrosion resistance and low neutron capture cross section, Zr alloys were considered for applications in breeder blanket designs some 20 years ago, and with the renaissance of interest in small fusion reactors in the UK are again being considered as possible materials for the UKAEA STEP programme. In the intervening period, a number of new Zr alloys have been developed for the environment of fusion reactors that could be assessed for higher temperature fusion applications, and there are several other binary Zr alloys systems that could be explored ab initio.

The project is divided into three main work packages. The first is the preparation and characterisation of a range of new Zr alloys, most of which have hardly been studied at all in previous literature. We have selected the Zr-Mo, Zr-Y, Zr-Al and Zr-V binary systems for immediate study because they offer the opportunity for metallurgical stability and so operation, at much higher temperatures than the conventional Zr-Nb or Zr-Sn fusion alloys. Other novel alloys systems can be added as appropriate during the project. These alloys will be cast and metallurgically processed by hot and cold rolling and heat treatments to give stable microstructures, characterised with analytical SEM and XRD, and the mechanical properties assessed as a function of temperature with micro-hardness, nano-indentation and small punch testing.
The second work package is to assess the corrosion resistance of these new alloys, and compare this to the performance of conventional fission alloys. High temperature water corrosion will be undertaken in autoclave facilities in the University of Manchester, and corrosion in liquid Li or PbLi alloys will be carried out in new facilities in Oxford.

The third work package is to study the radiation resistance of one or two of the most promising of these alloys based on the results of the first two work packages. Initially we will use proxy irradiation with light and heavy ions at the Dalton Cumbrian Facility to study microstructural modification and possible embrittlement processes at high damage levels. Later on in the project we plan to use the new national neutron source at Birmingham University to generate neutron damage, and the National Nuclear User Facilities on the Culham Campus (the Materials Research Facility) to study the mechanical properties of these radioactive samples.

The aim of the project is to identify one or two of the most promising alloy systems to recommend for further development as potential fusion materials. The novelty of the project lies in the exploration of the performance of some promising, but so far almost completely ignored, Zr alloy systems specifically for the conditions they will need to survive in fusion reactors. The project falls within the EPSRC Energy Theme; Research areas - Nuclear Fission and Magnetic Confinement Fusion Research Programme.